RE: [PATCH] EXTCON: Get and set cable properties

["Tc, Jenny" <jenny.tc@intel.com>]

> We discussed about this patch and then suggest some method to resolve this
> issue by Myungjoo Ham. Why don't you write additional feature or your
> opinion based on following patch by Myungjoo Ham?
> -
> http://git.kernel.org/?p=linux/kernel/git/mzx/extcon.git;a=commitdiff;h=73
> 12b79d69a2b9f06af4f1254bc4644751e3e3ea
> 

I replied on the thread and pointed out issues that I see with this solution. IMHO
It's not fair to register a cable with power_supply/regulator/charger manager just to
expose the cable properties. 

> 
> On 11/28/2012 06:49 AM, Jenny TC wrote:
> > Existing EXTCON implementation doesn't give a mechanim to read the
> > cable properties and extra states a cable needs to support. There are
> > scenarios where a cable can have more than two
> > states(CONNECT/DISCONNECT/SUSPEND/RESUME etc) and can have some
> > properties associated with cables(mA)
> >
> > This patch introduces interface to get and set cable properties from
> > EXTCON framework. The cable property can be set either by the extcon
> > cable provider or by other subsystems who know the cable properties
> > using eth API extcon_cable_set_data()
> >
> > When the consumer gets a notification from the extcon, it can use the
> > extcon_cable_get_data() to get the cable properties irrespective of
> > who provides the cable data.
> >
> > This gives a single interface for setting and getting the cable properties.
> >
> > Signed-off-by: Jenny TC <jenny.tc@intel.com>
> > ---
> >  drivers/extcon/extcon-class.c |   30
> ++++++++++++++++++++++++++++++
> >  include/linux/extcon.h        |   39
> +++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 69 insertions(+)
> >
> > diff --git a/drivers/extcon/extcon-class.c
> > b/drivers/extcon/extcon-class.c index d398821..304f343 100644
> > --- a/drivers/extcon/extcon-class.c
> > +++ b/drivers/extcon/extcon-class.c
> > @@ -545,6 +545,36 @@ int extcon_unregister_notifier(struct extcon_dev
> > *edev,  }  EXPORT_SYMBOL_GPL(extcon_unregister_notifier);
> >
> > +/**
> > + * extcon_cable_set_data() - Set the data structure for a cable
> > + * @edev:	the extcon device
> > + * @cable_index:	the cable index of the correspondant
> > + * @type:	type of the data structure
> > + * @data:
> > + */
> > +void extcon_cable_set_data(struct extcon_dev *edev, int cable_index,
> > +			   enum extcon_cable_name type,
> > +			   union extcon_cable_data data)
> > +{
> > +	edev->cables[cable_index].type = type;
> > +	edev->cables[cable_index].data = data; }
> > +
> > +/**
> > + * extcon_cable_get_data() - Get the data structure for a cable
> > + * @edev:	the extcon device
> > + * @cable_index:	the cable index of the correspondant
> > + * @type:	type of the data structure
> > + * @data:	the corresponding data structure (e.g., regulator)
> > + */
> > +void extcon_cable_get_data(struct extcon_dev *edev, int cable_index,
> > +			   enum extcon_cable_name *type,
> > +			   union extcon_cable_data *data)
> > +{
> > +	*type = edev->cables[cable_index].type;
> > +	*data = edev->cables[cable_index].data; }
> > +
> >  static struct device_attribute extcon_attrs[] = {
> >  	__ATTR(state, S_IRUGO | S_IWUSR, state_show, state_store),
> >  	__ATTR_RO(name),
> > diff --git a/include/linux/extcon.h b/include/linux/extcon.h index
> > 2c26c14..4556cc5 100644
> > --- a/include/linux/extcon.h
> > +++ b/include/linux/extcon.h
> > @@ -135,6 +135,19 @@ struct extcon_dev {
> >  	struct device_attribute *d_attrs_muex;  };
> >
> > +/* FIXME: Is this the right place for this structure definition?
> > + * Do we need to move it to power_supply.h?
> > + */
> > +struct extcon_chrgr_cable_props {
> > +	unsigned long state;
> > +	int mA;
> > +};
> 
> As I said, extcon provider driver didn't provide directly charging current(int
> mA) and some state(unsigned long state) because the extcon provider
> driver(Micro USB interface controller device or other device related to
> external connector) haven't mechanism which detect dynamically charging
> current immediately. If you wish to provide charging current data to extcon
> consumer driver or framework, you should use regulator/power_supply
> framework or other method in extcon provider driver.
> 
> The patch suggested by Myungjoo Ham define following struct:
> 	union extcon_cable_data {
> 		struct regualtor *reg;  /* EXTCON_CT_REGULATOR */
> 		struct power_supply *psy; /* EXTCON_CT_PSY */
> 		struct charger_cable *charger; /*
> EXTCON_CT_CHARGER_MANAGER */
> 		/* Please add accordingly with enum extcon_cable_type */
> 	};
> 
> Also if you want to define 'struct extcon_chrgr_cable_props', you should
> certainly show how detect dynamically charging current or state.
> 
> > +
> > +union extcon_cable_data {
> > +	struct extcon_chrgr_cable_props chrgr_cbl_props;
> > +	/* Please add accordingly*/
> > +};
> > +
> >  /**
> >   * struct extcon_cable	- An internal data for each cable of extcon
> device.
> >   * @edev	The extcon device
> > @@ -143,6 +156,8 @@ struct extcon_dev {
> >   * @attr_name	"name" sysfs entry
> >   * @attr_state	"state" sysfs entry
> >   * @attrs	Array pointing to attr_name and attr_state for attr_g
> > + * @type:	The type of @data.
> > + * @data:	The data structure representing the status and states of this
> cable.
> >   */
> >  struct extcon_cable {
> >  	struct extcon_dev *edev;
> > @@ -153,6 +168,11 @@ struct extcon_cable {
> >  	struct device_attribute attr_state;
> >
> >  	struct attribute *attrs[3]; /* to be fed to attr_g.attrs */
> > +
> > +	union extcon_cable_data data;
> > +
> > +	/* extcon cable type */
> > +	enum extcon_cable_name type;
> It isn't correct. The 'enum extocn_cable_name' isn't type. For example, the
> list of charger cable are TA/USB/Fast Charger/Slow Charger and so on.
> The charger cables are charger type so, they has
> EXTCON_CT_CHARGER_MANAGER as cable type.
> 
> The patch suggested by Myungjoo Ham define following struct:
> 	enum extcon_cable_type {
> 	       EXTCON_CT_NONE = 0,
> 	       EXTCON_CT_REGULATOR,
> 	       EXTCON_CT_PSY,
> 	       EXTCON_CT_CHARGER_MANAGER,
> 	       /* Please add other related standards when needed */
> 	};
>